Tetrarhodium dodecacarbonyl (RH.sub.4 (CO).sub.12) is a useful organometallic compound. It can be used as a catalyst or catalyst precursor in such processes as hydroformylation, hydrosilylation and carboxylation. While Rh.sub.4 (CO).sub.12 is a commercially available product, it is very expensive partly because of the difficulty of preparation.
A number of preparations of Rh.sub.4 (CO).sub.12 have been given in the literature. One is based on high pressure (3000 psig, 210.9 kg/cm.sup.2) starting from RhCl.sub.3 or Rh.sub.2 (CO).sub.4 Cl.sub.2 ; other procedures employing atmospheric pressure CO have been taught starting from Rh.sub.2 (CO).sub.4 Cl.sub.2, K.sub.3 (RhCl.sub.6) and RhCl.sub.3.xH.sub.2 O. The compounds Rh.sub.2 (CO).sub.4 Cl.sub.2 and K.sub.3 (RhCl.sub.6) would not be considered good starting materials from an economic standpoint. RhCl.sub.3.xH.sub.2 O is the most readily available starting material. The literature preparations* involve the use of specially treated solvents and the use of inert atmosphere e.g. CO gas padding of the reaction mixture during the product isolation. FNT *Martinengo, S.; Giordano, G. and P. Chini, Inorg. Synth. 1980, 20, 209.
It would be desirable if a simpler, less complicated and less time consuming process for the preparation of the tetrarhodium dodecacarbonyl could be found.
The present invention is such a process run at low pressures, requiring less time (ca. 2 hours) and does not require specially dried, purified, or deaerated solvents or CO atmosphere handling during the product isolation.